The present invention concerns methods which compensate for the differing heights of molds used in injection-molding machines, to thereby compensate the operation of control devices which operate in dependence upon mold height.
Injection-molding machines typically comprise two mold-clamping plates which face each other, one usually being stationary and the other shiftable to and from the first. The two mold halves of a split mold are mounted on respective ones of the mold-clamping plates, and the mold-clamping plates are brought together to close the mold and to apply the requisite clamping force. With the mold thusly closed, the plastified molding material is injected through an injection passage which passes through one mold-clamping plate, by the plastifying and injecting screws, into the hollow interior of the closed mold to injection-mold the molded item desired. Thereafter, the mold is opened, and the molded item clinging to one mold half is ejected therefrom by an ejecting device. The mold is then closed again, and the next molded item is injection-molded.
In particular, when the mold has been opened to a predetermined extent, there is generated a control signal for the ejecting device, so that the ejector pin will enter into the one mold half and push out the molded item therein. This control or command signal is generated in dependence upon the position of the shiftable one of the two mold-clamping plates. In general, when changing over from one mold to another, the new mold will have a different height, as measured in the direction in which the mold-clamping plates are spaced from each other. Accordingly, upon such mold changeover, the means producing this control or command signal in dependence upon clamping plate position must be readjusted, to take into account the new mold height. Thus, when a new mold has been inserted, the operator must first close the mold and very carefully reestablish the setting of the means generating the control or command signal in question; this must be done very carefully. In general many of the control signals for injection-molding devices are way-dependent signals e.g. signals dependent of the position of the shiftable plate. These signals must be modifed or corrected when another mold of other height is clamped onto the plates. The correction or modification of these way-dependent signals is performed according to the invention by an absolute coded angle indicator.